Questions about the DSP on the 4D/35...

[Mark Callow]

In article <9104241553.AA03446 at crow.omni.co>, rpaul at crow.UUCP (Rodian Paul) writes:
|> 
|> Hi, perhaps these questions are a little premature, but how are we going to be 
|> able to access the DSP in our 4D/35's? 
|> 
|> Will there be some kind of microcode compiler being released for it, or is SGI
|> going to supply some front-end libraries?
|> 
|> I'm not much up on DSP technology, but I seem to recall in a review I read
|> when the NeXT first came out that their DSP (same 56000 series I believe) 
|> can also be used to manipulate video signals. Will we be able to do this with 
|> the 35's? How about dumping our our Image-Processing kernels down etc.
|> 
|> Sorry if this info is allready in the brouchure, but I can't find our old 
|> spec-sheets around the office.
|> 

The DSP on the 4D/35 is intended as a co-processor to handle time
critical tasks such as getting audio sample bits pumped through the D-A
at the correct rate. The DSP will handle a number of system tasks of
a time critical nature: audio input, audio output, high speed serial
ports, and MIDI in/out through the serial ports.  By the time it gets done
with all this it will probably not have too many cycles left over.  We
will most likely also put the DSP to work on some audio channel mixing
and sample rate conversion tasks.

We will provide front end libraries to access the functionality we build into
the DSP.  We are not planning to allow arbitrary downloading of code
into the DSP.

This follows the model we've established with our graphics pipelines.
The Personal IRIS Turbo Graphics option even has a DSP that is used to
assist with pipeline processing.

Fear not.  The 4D/35 has a 36 MHz main cpu delivering roughly 33 mips.
The DSP runs at 20MHz and has (maybe) 16 MIPS.  So all those compute
intensive but not time critical tasks such as image processing and
video processing are best done on the main cpu.

Systems like the NeXT and Macintosh use DSP's for these kinds of tasks
because their DSP's are much faster than their main CPU's.
-- 
>From the TARDIS of Mark Callow
msc at ramoth.sgi.com, ...{ames,decwrl}!sgi!msc
"Spirits of genius are always opposed by mediocre minds" - Albert Einstein